Lubricating oil composition



, have the poorest viscosity characteristics.

Patented July 1 0,v 1945 Anthony H. Gleason, Westfleld, N. 1., assitnor to.

Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 1, 1943,

Serial No. 411,009

Claims.

invention relates to mineral lubricating oil compositions of good viscosity characteristics.

' The invention relates particularly to the preparation of improved lubricating compositions by' blending in petroleum lubricating oils compounds effective for reducing the viscosity temperature variation of the oil. One of the major properties required of a satisfactory lubricating composition is that of suitable viscosity. In order to be satisfactory for a lubrication service such as in an automobile engine, the oil must have a suitable viscosity at normal atmospheric temperatures and a relatively small rate of change of viscosity with temperature in order to avoid any strain upon the parts as in the engine in starting or. high temperature operating.

' Change in viscosity with temperature is of great importance. Although the S. A. E. number of an oil indicates its approximate viscosity at aparticular temperature, it furnishes no indication as to what the viscosity will be at any other temperature. One method in common use for indicating the viscosity-temperature relationship is known as the viscosity indexscale as proposed by Dean and Davis in Chemical and Metallurgical Engineering, volume 36, Page 618 (1929) If an oil has a'low viscosity index, that is, changes rapidly with changes in temperature, 'it

" may be viscous'enough to function satisfactorily atone temperature and then be totally unsatisfactory at a higher temperature due to a marked decrease in viscosity or thinning out. In addition, the same oil may be so viscous at low temperatures that it would be diflicult or impossible to move the lubricating oil through the engine parts with the power available, Obviously a high viscosity index, that is a relatively low rate of change of viscosity with temperature, is particularly important in the case of automobile crank case lubricants. With such lubricants, it is desirable to have a lubricant which will not be too viscous for cold weather starting and at the same time will not thin out excessively after the engine has become heated up. v

Of the various types of lubricating oil distillates derived from crudes. those obtained from Pennsylvania stocks have the best general viscosity characteristics, while those from Coastal crudes However, by a suitable means of refining, improvement in all-around viscosity characteristics can be obtained upon both types of distillates, as well as those of the intermediate type known as the Mid-Continent type. Refining to improve viscosity index to any marked extent as for example by means of solvent extraction is generally costly.

In addition, if oils are over refined by this method, they tend to be less stable to oxidation and more corrosive toward hard alloy bearings. For these reasons, it is generally preferable to employ conventional refining to remove colorand-sludge impurities and, if desired, mildly solvent-extract the oils and then to effect further improvement of the oil by the addition of small percentages of compounds for raising the viscosity index.

The present invention relates to the art of improving refined lubricating oils by the blending therein of additives especially effective in improving the viscosity-temperature relationship. ,Thus the invention is concerned with the preparation of high quality lubricating compositions. These compositions are prepared by the addition of suitable viscosity-index-improving materials to all types of mineral oil distillates, no matter how extensively refined. The compositions so prepared are particularly adapted for the lubrication of automobile and similarly related mechanical systems. Vegetable oils may also be-similarly improved by the blending therein of the additives of this invention.

In the prior art, viscosity improvement of lubricating oils has been eflected by the addition of polymerized hydrocarbon materials. These materials are effective in relatively small amounts. Moreover, they are stable under conditions of use and are satisfactorily soluble in mineral lubricating oils.

weight compounds produced by condensation reactions, namely, those of certain phenolic derivatives of aliphatic acids. The addition of such compounds in amounts between 0.5% and 7% by weight, and preferably 0.75% to 5.0% by weight,

to lubricating oils is the subject matter of the present invention.

The condensed phenolic derivatives of the aliphatic acids employed in this invention are essentially high molecular weight esters. These polyester type addition agents are obtained from compounds of the type I noncH. .cooH

Such properties have been found to be also characteristic of a series of high molecular inert gas such as nitrogen or hydrogen. The passage of the gas through the mixture facilitates the removal of the water produced in the reaction and shortens the reaction period. The formation of compounds having suitable molecular weights in the range of 5,000 to 20,000 may be obtained under such conditions with the reaction period varying from one day to four days. Thefinal product is generally considered to be a linear polymer with recurring side chains represented by the groups Rin the following general formula:

(-OO-CH-(cmilL) i. In this invention it is preferable that R in the above general formula be at least an-ethyl group, that .is, contain at least 2 carbon atoms in the grouping. It is also considered preferable that B should not contain more than about 20 carbon atoms.

' The monomeric phenolic acids employed as the basicrea'ctants in the preparation of the lubricating oil addition agent of this invention may be prepared by the hydrolysis of the' halogen derivatives of phenyl substituted fatty acids, the halogen being a nuclear substituent. Thus. -hydroxy pheny1 stearic acid may be prepared by the hydrolysis of IO-bromo phenyl stearic acid at 280 C. R in this instance is an 8-carbon atom chain, and imparts excellent oil solubility to the resultant polymer product. Other suitable hydroxy phenyl substituted acids may be prepared from the interaction of myristolenic acid and erucic acid with a halogenated benzene such as either chlorobenzene or bromobenzene and subsequently hydrolyzing the resultant product. Another suitable monomeric material may be prepared by the treatment of castor oil to obtain undecylenic acid, then reacting this material with. either chlorobenzene or bromobenzene. eflected between, the undecylenicacid and bromobenzene to form the phenolic substituted acid, the R would be either a. hydrogen atom or a methyl group. Other preferred compounds to be subjected to autocondensation for the purposes of this invention are 10-hydroxy-phenyl .myristic acid and 13-hydroxy-phenyl behenic acid.

Other halo-phenol substituted fatty acids may be prepared by the interaction of alkyl substituted halo-benzenes, such as chlorotoluene or chlorobutylbenzene; Such compounds would give rise to products of the general formula in which R is an alkyl group. If either-R or R contains about 6 carbon atoms in their groupings, the resultant polymer product has the desired oil solubility to -be a satisfactory mineral lubricating oil addition agent. may be either hydrogen atoms oraliql groupings; provided in their sum sufficient carbon atoms are present in alkyl groupings, that is. between about 6 and carbon atoms, to impart satisfactory oil solubility.

' An additive agent according to the present invention was prepared by heating lO-hydroxy phenyl stearic acid for 4 days at between 210' C.

- viscosity index improver:

and 220 C., while dry hydrogen was passed through the mixture. The product was blended in 5% concentration in an S. A. E. 20W mineral lubricating oil and the viscosity characteristics of the blended oil compared with those of the base oil. Data which are presented below show that the additive was markedly effective as a Saybolt Sayboit Material vis. vis. V. I.

i 100 F. 210 F.

Mineral oil s. A. neow 276.8 45. o Mineral oil 8. A. E. 20W+5% polyester. 464. 5 56 61 It is obvious that the potency of the polyester as a V- I. improver depends greatly on its molecu- -lar weight and the latter will depend largely on the purity of the original monomeric compound. The presence of simple phenols or fatty acids will automatically limit the molecular weight by interrupting the condensation. It is not desirable to employ polymers with molecular weights greatly in excess of 20,000. Polymeric compounds having molecular weights much in excess of 20,000 undergo mechanical break down with a'resultant loss of viscosity during -use and a lowering of the viscosity index of the merely for the purpose of explaining and illus- In this latter case, if the reaction is trating the invention. It is believed obvious that modifications and variations may be made from that described and illustrated. Such variations are believed within the scope ofthc invention.

eral lubricating oil and a high molecular weight polyester derivative of a phenyl-hydroxy derivative of an unesterified aliphatic acid, said polyester derivative being present in amount effective to favorably-influence the viscosity-temperature Thus, R and R l relationships of the oil, and having a molecular polymer of a phenol substituted fatty acid.

4. A lubricating composition according to claim 2 in which the high molecular weight polyester is' present from 0.5 to 7.0% by weight of the mineral lubricating oil.

5. A lubricating composition comprising a mineral lubricating oil and between 0.5% and 7.0% by weight of a linear polyester compound formed by the autocondensation of a phenyl-hydroxy derivative of an aliphatic acid of general formula which Rand R are alkyl radicals the sum of which contains between 6 and 20 carbon atoms and a: is an integer greater than 4, said polyester compound having a molecular weight not greatly in excess of 20,000.

-6. A lubricating composition comprising a mineral lubricating oil and 0.75% to 5% by weight of a high molecular weight polyester formed by the autocondensation at about 210 C, of lo-hydroxyphenyl myristic acid, said polyester having a molecular weight not greatly in excess of 20,000.

'7. A lubricating composition comprising a mineral lubricating oil and 0.75% to 5% by weight of a high molecular weight polyester formed by 'the autocondensation at about 210 C. of-13- hydroxy-phenyl behenic acid, said polyester having a molecular weight not greatly in excess of 20,000.

8. A lubricating composition comprising a mineral lubricating oil and 0.75% to 5% by weight of a high molecular weight polyester formed by the autocundensatlon at about 210 C. of 10-hydroxyphenyl stearic acid, said polyester having a molecular weight not greatly in excess of 20,000

. 9. A lubricating composition containing a mineral lubricating oil and a small quantity of a high molecular weight linear, recurring side chain polyester derivative of an unesterified aliphatic acid, said polyester having a phenolic group recurring in the linear portion of the polyester, and a molecular weight not greatly in excess of 20,000.

10." A lubricating, composition according to claim 9, in whl'ch' the acid' is monomeric and unhydroxylatedl i ANTHONY H. GLEASONr- 

